completely understood, it seems entirely prob- 

 able that to understand an organism's response 

 to temperature at a contemporary instant we 

 must consider in addition to absolute tempera- 

 tures the derivatives with respect to time and 

 space of temperature. Even in a simplified 

 univariate situation a knowledge of the thermal 

 history of a fish would be difficult to obtain. 



Despite the difficulty in obtaining information 

 on acclimatization it appears that this phenom- 

 enon may very well operate in tunas and may 

 provide at least a partial explanation for the 

 albacore being taken in waters of the Japanese 

 fishery that are several degrees cooler than 

 those in which they are taken in the North 

 American fishery. Even within the eastern 

 Pacific fishery the apparent temperature pref- 

 erendum appears to be related to the size of 

 the albacore. The differences in apparent tem- 

 perature at different locations and at different 

 sizes or ages are probably related, to some ex- 

 tent, to acclimatization phenomena. Thus, with 

 even a variable that is as relatively simple to 

 measure as temperature, many conceptual prob- 

 lems still need to be resolved in order to under- 

 stand the causal nature of spatial distributions 

 with respect to temperatures and other environ- 

 mental or sets of environmental variables. 



Migratory Route 



An understanding of the migratory route of 

 the albacore among the three fisheries of the 

 North Pacific Ocean is of crucial importance to 

 understanding the dynamics of the albacore. 

 Knowledge of the migratory route is needed to 

 estimate age-specific fishing mortality and 

 also to understand the manner in which events 

 in each fishery affect events in other fisheries. 

 For example, if, as we postulate in this paper, 

 an important segment of the albacore escape- 

 ment from the North American fishery becomes 

 vulnerable to the pole-and-line fishery before 

 it becomes vulnerable to the longline fishery, 

 then an understanding of the changes in abun- 

 dance, and the amount of fishing effort exerted 

 in the pole-and-line fishery is crucial to ob- 

 taining an understanding of the causes of the 

 decline in apparent abundance in the longline 

 fishery. Another example of how the dynamics 

 of the albacore in one fishery might affect the 

 dynamics of the albacore in another fishery is 

 provided by data given in Clemens and Craig 

 (1965). If we take their data at face value, we 

 find that in their figure 96, the California 

 fishery after 1950 exhibits (1) a decreasing 



trend in catch, (2) a decreasing trend in effort 

 measured in number of boat-months and in 

 number of boats, and (3) an increasing trend in 

 catch per boat-month. For steady-state re- 

 cruitment into the California fishery and no 

 trends in catchability coefficient, etc., their 

 data imply an increasing trend in escapement 

 from the California fishery. If, in fact, there 

 is an increasing trend in escapement and all 

 other things are equal, the recruitment to the 

 Japanese fisheries must be increasing. We 

 conclude (on the basis of accepting the simpli- 

 fying assumptions that catchability for the Cal- 

 ifornia fishery is constant, etc.) that a consid- 

 eration of a declining apparent abundance of the 

 longline fishery must include the evidence that 

 this decline occurs in the face of an increasing 

 trend in recruitment to the Japanese fisheries. 

 This consideration must also include an under- 

 standing of the predominant route of the alba- 

 core because the effort of an increasing trend 

 in recruitment to the Japanese fisheries upon 

 the longline fishery would depend, to a large 

 extent, on whether the recruited fish first enter 

 the longline or the pole-and-line fishery. 



Although we have emphasized the North Amer- 

 ican to pole-and-line to longline migratory 

 route we should stress that the reasoning that 

 we have used to support this pathway has a 

 possible internal inconsistency. This incon- 

 sistency arises between the migratory-route 

 evidence based upon the relation of time be- 

 tween middates of each fishery and growth 

 estimates (fig. 18) and the ratio of longline to 

 pole-and-line tag recoveries (fig. 16). The 

 good agreement between the expected sizes 

 based on middates between fisheries and growth 

 rate and the actual average size depicted in 

 figure 5 suggests that the entry of any albacore 

 into the longline fishery before the pole-and- 

 line fishery is unlikely. On the other hand, the 

 rather limited tagging data indicate that some- 

 what less than half of the albacore enter the 

 longline fishery before the pole-and-line fish- 

 ery, implying that the longline fish should have 

 an average length of about 81 cm. Since our 

 information on average size, growth rates, 

 middates of fishery, and proportion of tag re- 

 coveries is collectively not very precise, an 

 interpretation of this possible inconsistency 

 must await further study. 



Evolution of Migratory Pattern 



The apparently well-defined migratory route 

 of the albacore invites speculation on themech- 



32 



